Aldehyde-functionalized polymers based on polyacrylamide (and similar polymers), provide a multitude of benefits for paper and paperboard manufacturing that include temporary wet strength, dry strength, wet-web strength, Yankee dryer adhesives, and increased press dewatering. Although benefits of such products are well established, the polymers suffer from instability towards gelling resulting in short shelf lives and low actives concentrations. This instability limits their use under some circumstances, presents significant logistical issues of storage and shipping, and results in lost batches that require disposal. Additionally, the stability of these polymers is sensitive to actives concentrations, and achieving acceptable shelf life necessitates low actives concentrations, which in turn increases costs of manufacture and shipping as well as requiring increased storage space.
U.S. patent application Ser. No. 10/785,403, “Glyoxylated Polyacrylamide Composition Strengthening Agent,” discloses an acidified glyoxalated polyacrylamide dosed with additional glyoxal. U.S. patent application Ser. No. 12/138,766, “High Solids Glyoxalated Polyacrylamide,” discloses stabilized glyoxalated polyacrylamide compositions having a high concentration of polymer solids.
A demonstrated need therefore exists for formulations of aldehyde-functionalized polymers based on polyacrylamide with improved stability and increased shelf-life. For these reasons, increased stability of such polymers is desirable to extend the product shelf life at fixed actives or to increase the actives concentrations at fixed shelf life. Longer shelf life is particularly desired in papermaking circumstances where such polymers are not continuously run, but are run only on selected grades. In addition, increased shelf life is desirable where long shipping distances are encountered due to lack of manufacturing facilities at point of use.